As the unit device (or cell) efficiency of an organic solar cell has been increased so that it is now commercially available, researches into an organic solar cell module in which solar cells are continuously connected are actively proceeding.
In particular, since an organic solar cell allows for utilization of a solution of an organic material, studies for introducing a printing process into the manufacture of an organic solar cell module to produce a low-cost organic solar cell module are attracting attentions.
The most widely used conventional organic solar cell module has the form where a patterned first electrode, a patterned first charge transport layer (hole transport layer or electron transport layer), a patterned photoactive layer, a patterned second charge transport layer (electron transport layer or hole transport layer) and a patterned second electrode are sequentially stacked on a substrate in this order.
In the conventional organic solar cell module, thin films should be formed by slightly shifting each layer to continuously connect counter electrodes each of which is in a different solar cell. In doing so, if counter electrodes in one solar cell contact with each other, it is no longer operate as a module.
Therefore, in the conventional organic solar cell module, the first charge transport layer, the photoactive layer and the second charge transport layer, as well as the first electrode and the second electrode, should be patterned, which means that a first electrode of a first organic solar cell directly contacts with a second electrode of a second organic solar cell without the hindrance of any other layer.
However, in the manufacture of the conventional organic solar cell module, since thin films should be patterned with slight and gradual shift of each layer, an advanced patterning technique is required to align thin films so as to obtain thus-patterned thin films, resulting in the difficulties in manufacturing an organic solar cell module and, consequently, the increase of the price of an organic solar cell module.
Further, as the number of such patterning processes increases, the active area (the area where an electric energy may be actually generated), i.e., the part where a first electrode and a second electrode of each solar cell are overlapped with each other, decreases, and the inactive area, i.e., the part where electrodes are not overlapped with each other, increases at the same time.
Thus, there is a problem that the dead zone (the area where an electric energy may not be actually generated) increases in the total solar cell area, resulting in the reduced efficiency of the solar cell module.